Abstract: The giant panda is an iconic and threatened species for wildlife conservation in China. Baylisascaris schroederi is the most common intestinal parasite found in the giant panda and represents a significant threat to both wild and captive populations. Given that giant pandas are geographically and genetically distinct and that there often is co-evolution between parasites and hosts, whether the evolution of B. schroederi correlates with the evolution of giant pandas has been, and is still, a matter of controversy. In this study, 34 B. schroederi isolates from two main giant panda populations distributed in Minshan (14) and Qionglai (20) mountain ranges, respectively, were subjected to analysis of population genetic diversities in terms of the complete mitochondrial 12S genes. Results showed that (1) a total of nine haplotypes were detected in the 34 isolates, with high haplotype diversity and low nucleotide diversity; (2) the negative neutrality tests (Tajima’s D and Fu's Fs) and mismatch analysis indicated that B. schroederi experienced a temporary population expansion in the recent past; (3) the low Gst and high Nm values suggested a low genetic variability between Minshan and Qionglai populations; additionally, (4) the phylogenetic tree and network map exhibited a mixed population distribution without area-originated specificity. Collectively, B. schroederi across Minshan and Qionglai exhibited an insignificant genetic differentiation and had low genetic diversities between them. This finding implies different evolutionary rates between B. schroederi and pandas, and the results should contribute to the control of B. schroederi in different mountain-range pandas.

Key words: Baylisascaris schroederi, Conservation ecology, Genetic diversity, Giant pandas, Mitochondrial 12S, Phylogeography

摘要： 大熊猫是中国特有的珍稀濒危物种，而西氏贝蛔虫是大熊猫体内最为常见的肠道寄生虫，对野生和圈养大熊猫危害极大。考虑到大熊猫因分布区域的差异而形成了不同的亚种以及寄生虫与宿主间广泛的协同进化关系，西氏贝蛔虫是否也存在与大熊猫相适应的亚种分化一直是野生动物学家极其关注和热议的话题。为此，本文选择中国两大山系（岷山和邛崃）大熊猫种群体内共计34株西氏贝蛔虫虫体样本进行种群遗传多态性研究。利用PCR技术扩增出了岷山（14株）和邛崃（20株）西氏贝蛔虫的线粒体12S基因全序列并对其做了遗传多样性分析。结果表明：（1）34个样本包含9个单倍型，呈现出一个高单倍性多样性和低核苷酸多样性的特点；（2）负的Tajima's D和Fu's Fs中性检验值及“多峰型”的种群歧点分布图暗示种群不久前曾经历过突增长的现象；（3）低的种群间的分化系数和高的基因流表明两个地理种群间未形成显著的遗传分化；（4）系统发育树和单倍型网络图表明两山系种群分布无区域特异性。因此，岷山和邛崃山系的大熊猫体内的西氏贝蛔虫种群遗传变异性较低，分化不明显。该发现不仅暗示了西氏贝蛔虫与其宿主（大熊猫）的进化不同步，而且还为不同区域大熊猫西氏贝蛔虫病的监控提供了理论依据。

关键词: 大熊猫, 西氏贝蛔虫, 种群遗传多样性, 线粒体12S, 地理位置多态性, 保护生态学